Manual focus device and autofocus camera

ABSTRACT

A digital still camera includes an aperture stop opening, a taking lens system, and a CCD pickup element. In a manual focus device, an iris shifting mechanism sets the aperture stop opening in an aperture stop unit with reference to a first light amount gravity center by shifting the aperture stop opening to the right relative to a lens optical axis, and sets the aperture stop opening with reference to a second light amount gravity center by shifting the aperture stop opening to the left. First and second sample pickup data are obtained by the CCD pickup element in the setting of the aperture stop opening at the two light amount gravity centers. A display panel displays first and second sample images according to the sample pickup data, to indicate a present deviation of the taking lens system from an in-focus position in simulation. A focusing ring is externally operable, for moving the taking lens system on the optical axis, and for actuation while the two sample images are checked visually, to position the taking lens system when the two sample images inform a reach to the in-focus position.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a manual focus device and autofocuscamera. More particularly, the present invention relates to a manualfocus device and autofocus camera in which an in-focus state can beindicated and focusing can be easily effected.

2. Description Related to the Prior Art

Rangefinder incorporated cameras are well-known in the art of camera, inwhich a rangefinder of a double image coincidence type or a verticalimage coincidence type is incorporated in a viewfinder. In therangefinder incorporated camera, changes in a focused state due tofocusing operation is observed as changes in a deviation between objectimages. Focusing with high precision is possible by observation with ahuman eye. The double image coincidence type of viewfinder has a viewfield where double images having an image through the viewfinder and animage through the rangefinder are observed. For focusing, the imagethrough the rangefinder moving according to the focusing operation isadjusted and caused to coincide with the image through the viewfinder.The vertical image coincidence type of viewfinder uses a micro splitimage prism disposed in a light path in the viewfinder, and forms upperand lower split images of the object in a partial view field of theviewfinder. The upper and lower split images are moved horizontally in asymmetrical manner according to focusing operation. If an in-focus stateis obtained, the split images coincide with one another.

There is a suggested structure of the viewfinder in JP-A 9-214813 and2001-309210 in which an electronically photographed object image isutilized for focusing instead of incorporating the rangefinder foroptically forming a double image or split images. According to this,double object images deviated according to a defocus amount areindicated with movement according to operation of focusing. It ispossible to save and reduce a space and cost by reducing the number ofparts for the optical structure.

For the purpose of the display of an image with movement in response tofocusing and the display of coincidence of images at the time of thein-focus state, it is necessary to predetermine a defocus amount.According to the prior art, there are generally known methods includinga triangulation method and a phase difference detection method. In thetriangulation method, an object distance is measured by use ofprojecting and detecting infrared rays in order to calculate the defocusamount. In the phase difference detection method, two line sensors areused to receive object light through light paths symmetrical to eachother with respect to the photographic optical axis, so as to calculatethe defocus amount according to a phase difference between photoelectricsignals from the line sensors.

Furthermore, an autofocus camera is well-known in which focusing isautomatically effected. One example of autofocus camera includes anactive type of rangefinder for projecting infrared rays. Another exampleof autofocus camera includes a passive type of rangefinder for utilizingobject light. The rangefinder of any of those types operates accordingto the rangefinding of triangulation, in which an object distance ismeasured to obtain an in-focus position of a focusing lens for thepurpose of focusing. Also, a digital still camera, video camera andother electronic equipment for photographing an image are known as theautofocus camera. A pickup element such as a CCD image sensor isutilized for picking up the object image. A contrast value is retrievedfrom the object image, and evaluated between pixels in each of frames.The focusing operation is automatically effected by obtaining a mosthighly sharpened contrast.

U.S. Pat. No. 6,453,124 (corresponding to JP-A 2001-281530) disclosesthe autofocus camera having a combined structure for focusing accordingto the contrast evaluation method and for focusing according to thephase difference detection method. In the phase difference detectionmethod, the phase difference is detected between photoelectric signalsof object light at points in two light paths which are symmetrical withrespect to the photographic light axis, so an in-focus position can bedetermined by instantaneously obtaining an amount of defocus accordingto the phase difference. In this prior document, the lens is focusedpreliminarily according to the detection of the phase difference. Afterthis, the lens is precisely focused by utilizing the evaluation of thecontrast. This construction is effective in raising the speed offocusing operation without lowering the precision.

However, there occurs a high rise in the manufacturing cost for theconstruction to calculate the defocus amount according to thetriangulation method. This is because of electric parts including thepickup element, a light projecting element for active rangefinding, aposition detecting element and the like which require high precision inthe incorporation. Similarly, the phase difference detection methodrequires a high manufacturing cost, because of an optical system forsplitting and introducing object light, a line sensor, and otherrelevant elements.

SUMMARY OF THE INVENTION

In view of the foregoing problems, an object of the present invention isto provide a manual focus device and autofocus camera in which anin-focus state can be indicated and focusing can be easily effected.

In order to achieve the above and other objects and advantages of thisinvention, a manual focus device for a camera is provided, the cameraincluding an aperture stop opening for introducing object light along alens optical axis, and limiting a light amount of the object light, ataking lens system, having a focusing lens movable on the lens opticalaxis, set in an in-focus position to focus the object light on a focalplane, a pickup element, disposed on the focal plane, for outputtingpickup data by picking up the object light. The manual focus deviceincludes an aperture stop shifting mechanism for setting the aperturestop opening with reference to a first light amount gravity center byshifting the aperture stop opening in a first direction relative to thelens optical axis, and for setting the aperture stop opening withreference to a second light amount gravity center by shifting theaperture stop opening in a second direction reverse to the firstdirection relative to the lens optical axis, the first and second lightamount gravity centers being equidistant from the lens optical axis. Animage memory stores first and second sample pickup data obtained bypicking up the object light on the pickup element when the aperture stopopening is set with reference to respectively the first and second lightamount gravity centers. A display panel displays first and second sampleimages in combination according to the first and second sample pickupdata, to indicate a present deviation of the focusing lens from thein-focus position in simulation. A lens driving mechanism is externallyoperable, for moving the focusing lens on the lens optical axis, and foractuation while the first and second sample images are checked visually,to position the focusing lens when the first and second sample imagesinform a reach to the in-focus position.

The aperture stop shifting mechanism further changes a diameter of theaperture stop opening about the lens optical axis, to adjust the lightamount for an exposure.

The first sample image has a form by shifting of an image represented bythe pickup image in one of the first and second directions according tothe present deviation of the focusing lens, the second sample image issymmetrical with the first sample image with respect to a center line ofthe image represented by the pickup image, and the first and secondsample images become positioned with coincidence when the focusing lensis in the in-focus position.

The aperture stop shifting mechanism includes first and second aperturestop blades, having curved inner edges opposed to each other, fordefining the aperture stop opening inside. First and second bladeactuators shift respectively the first and second aperture stop bladesin the first or second direction.

A frame of the display panel includes first and second split regionsbeing partial, and a main region or background region formed outside thefirst and second split regions. The image memory stores data of thefirst and second sample images obtained by subjecting the first andsecond sample pickup data to trimming processing according to the firstand second split regions. Furthermore, a main image memory stores dataof an object image obtained by subjecting the pickup data to trimmingprocessing according to the background region.

The first and second directions are horizontal, and the first and secondsplit regions are adjacent vertically with one another.

The first and second split regions are located at a center of thebackground region, or near to the center.

The display panel is constituted by a viewfinder for observing anobject.

In a preferred embodiment, the camera further comprises a viewfinder forobserving an object. The display panel is disposed in a rear of thecamera and under the viewfinder.

Furthermore, a defocus determiner processes the first and second samplepickup data in a phase difference detection processing, and obtainsdefocus information of the present deviation of the focusing lens fromthe in-focus position.

Furthermore, a shifting amount detector detects a shifting amount of thelens driving mechanism. An image outputting circuit corrects the firstand second sample images on the display panel according to the shiftingamount of the lens driving mechanism. When the shifting amount comes upto a value corresponding to the defocus information, the first andsecond sample images inform the reach to the in-focus position.

Furthermore, a gain controller amplifies the pickup data inconsideration of a predetermined brightness level.

The gain controller further obtains pixel mixing pickup data byobtaining an arithmetic average of the pickup data of N adjacent pixels,and substitutes the pixel mixing pickup data for the pickup data of theN adjacent pixels, whereby the pixel mixing pickup data is provided withN times as high contrast as the pickup data.

Furthermore, a mode switch is turned on to set a high contrast mode.When the high contrast mode is set, the gain controller obtains thepixel mixing pickup data to provide high contrast.

When the aperture stop shifting mechanism is set at the first and secondlight amount gravity centers, a diameter of the aperture stop opening issmaller than a diameter of the aperture stop opening in a fully openstate.

According to one aspect of the invention, an autofocus camera includes ataking lens system, having a focusing lens set in an in-focus positionon a lens optical axis, for focusing object light on a focal plane. Alens driving mechanism moves the focusing lens on the lens optical axis.A pickup element is disposed on the focal plane, for outputting pickupdata by picking up the object light. An aperture stop opening introducesthe object light along the lens optical axis, and limits a light amountof the object light. An aperture stop shifting mechanism sets theaperture stop opening with reference to a first light amount gravitycenter by shifting the aperture stop opening in a first directionrelative to the lens optical axis, and sets the aperture stop openingwith reference to a second light amount gravity center by shifting theaperture stop opening in a second direction reverse to the firstdirection relative to the lens optical axis, the first and second lightamount gravity centers being equidistant from the lens optical axis. Acontroller outputs first and second sample pickup data obtained bypicking up the object light on the pickup element when the aperture stopopening is set with reference to respectively the first and second lightamount gravity centers, obtains an in-focus position by a process ofcomparison and evaluation of the first and second sample pickup data,and drives the lens driving mechanism in accordance therewith.

The controller includes an image comparator for operating in a phasedifference detection processing, to obtain a phase difference detectionprocessing result by comparison between the first and second samplepickup data. A defocus determiner obtains defocus information to movethe focusing lens to the in-focus position according to the phasedifference detection processing result.

Furthermore, a comparator determines whether brightness according to thepickup data is a low brightness by comparison with threshold data. Whenthe brightness according to the pickup data is the low brightness, thegain controller amplifies the first and second sample pickup data.

Furthermore, a comparator determines whether brightness according to thepickup data is a low brightness by comparison with threshold data. Acontrast determiner outputs contrast distribution information accordingto the pickup data. When the brightness according to the pickup data isthe low brightness, the controller inhibits the aperture stop shiftingmechanism from shifting toward the first and second light amount gravitycenters, causes the aperture stop shifting mechanism to open fully theaperture stop opening, moves the focusing lens, and checks a change inthe contrast distribution information in moving the focusing lens, todetermine the in-focus position in accordance therewith.

The contrast distribution information is a finite difference betweenmaximum and minimum brightness levels of an image according to thepickup data, and when the finite difference is greatest, then thefocusing lens is judged as set in the in-focus position.

Furthermore, a temporary memory stores preceding pickup data prior tothe pickup data from the pickup element, and stores the pickup data inresponse to a change in an output of the pickup element by overwritingwith the preceding pickup data. The image comparator further checks theoutput change of the pickup element in a time-sequential manner, andcompares the pickup data with the preceding pickup data, to outputtime-sequential comparison information. An image shake compensatorsubjects the pickup data to image shake compensation according to thecomparison information.

According to another aspect of the invention, an autofocus camera has anaperture stop shifting mechanism for setting the aperture stop openingwith reference to a first light amount gravity center by shifting theaperture stop opening in a first direction relative to the lens opticalaxis, and for setting the aperture stop opening with reference to asecond light amount gravity center by shifting the aperture stop openingin a second direction reverse to the first direction relative to thelens optical axis, the first and second light amount gravity centersbeing equidistant from the lens optical axis. An aperture stop shiftingcircuit controls the aperture stop shifting mechanism sequentially infirst, second and third shifting steps, wherein the aperture stopshifting circuit, when in the first shifting step, sets the aperturestop opening with reference to the first light amount gravity center,then shifts and sets the aperture stop opening with reference to thesecond light amount gravity center, the aperture stop shifting circuit,when in the second shifting step, shifts the aperture stop opening inthe first direction from the second light amount gravity center, theaperture stop shifting circuit, when in the third shifting step, setsthe aperture stop opening with reference to the first light amountgravity center, then shifts and sets the aperture stop opening withreference to the second light amount gravity center. A controlleroutputs first and second sample pickup data associated with respectivelythe first and second light amount gravity centers during the firstshifting step by picking up the object light in the pickup element,outputs third and fourth sample pickup data associated with respectivelythe first and second light amount gravity centers during the thirdshifting step by picking up the object light in the pickup element,determines a first deviation between the first and second sample pickupdata or between the third and fourth sample pickup data, determines asecond deviation between the first and third sample pickup data orbetween the second and fourth sample pickup data, determines a finitedifference between the first and second deviations, determines thein-focus position by evaluating the finite difference, and causes thelens driving mechanism to move the focusing lens to the in-focusposition.

The aperture stop shifting circuit is so constructed that the first,second and third shifting steps take time of lengths equal to oneanother.

BRIEF DESCRIPTION OF THE DRAWINGS

The above objects and advantages of the present invention will becomemore apparent from the following detailed description when read inconnection with the accompanying drawings, in which:

FIG. 1 is a perspective illustrating a manual focus type of digitalstill camera;

FIG. 2 is a rear perspective illustrating the camera;

FIG. 3 is a block diagram schematically illustrating the camera;

FIG. 4 is an exploded perspective illustrating an iris driving mechanismin the camera;

FIG. 5A is an explanatory view illustrating an image deviation caused bya shift of an aperture stop opening to the right;

FIG. 5B is an explanatory view illustrating an image deviation caused bya shift of an aperture stop opening to the left;

FIG. 6A is an explanatory view illustrating an in-focus state with apath of light without image deviation;

FIG. 6B is an explanatory view illustrating a front focus state and asize of an image deviation;

FIG. 6C is an explanatory view illustrating a rear focus state and asize of an image deviation;

FIG. 7 is a block diagram schematically illustrating a pickup dataprocessor;

FIG. 8 is an explanatory view illustrating a series of various imagescombined in the camera, including a completed state of an image on adisplay panel;

FIG. 9 is a flow chart illustrating a process of focus adjustment andpickup;

FIG. 10 is a block diagram schematically illustrating an autofocus typeof digital still camera according to one preferred embodiment;

FIG. 11 is a block diagram schematically illustrating a pickup dataprocessor in the autofocus camera;

FIG. 12 is a flow chart illustrating a process of focus adjustment andpickup;

FIG. 13 is a perspective illustrating another preferred iris drivingmechanism;

FIG. 14 is a block diagram schematically illustrating another preferredautofocus camera suitable for a moving object;

FIG. 15 is a flow chart illustrating a process of focus adjustment andpickup;

FIG. 16 is a explanatory view illustrating a series of sample pickupimages for the purpose of focusing; and

FIG. 17 is a graph illustrating positions of the moving object picked upwith reference to elapsed time.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT(S) OF THE PRESENTINVENTION

In FIG. 1, a digital still camera 1 of the invention is constituted by alens barrel 3, a grip 4, a release button 5 and a mode selection dial 6as mode switch. A taking lens system 2 is mounted in the lens barrel 3.The release button 5 has a construction depressible in a halfway stepand a fully depressed step. A focusing ring 7 of a focusing lens drivingmechanism is disposed around the lens barrel 3, and rotatable forfocusing the taking lens system 2 to a photographic object.

In FIG. 2, the rear of the digital still camera 1 has a back monitordisplay panel 8 and a viewfinder 9 with a display panel. The monitordisplay panel 8 is a liquid crystal display panel of a full-color typeto indicate an object image. Also, a small type of a color liquidcrystal display panel is incorporated in the viewfinder 9. The monitordisplay panel 8 and the viewfinder 9 are controlled for selectiveoperation. When the viewfinder 9 is used, the monitor display panel 8 iskept turned off forcibly. The use of the viewfinder 9 makes it possibleto save power effectively in comparison with the use of the monitordisplay panel 8.

In FIG. 3, the digital still camera 1 includes a main controller 11, apickup data processor 12, a display controller 13 and an image memory14. The main controller 11 operates according to pre-programmedsequences, outputs control signals to relevant sections, andadministrates electric operation of the camera. The pickup dataprocessor 12 is supplied by a CCD pickup unit 15 with pickup data, andsubjects the pickup data to amplification and image processing. Thedisplay controller 13 outputs an image of a photographic object fordisplay in the monitor display panel 8 or the viewfinder 9 as a smallmonitor. The image memory 14 stores image data according to the pickupdata output by the pickup data processor 12 upon a full depression ofthe release button 5.

The CCD pickup unit 15 is constituted by a zoom lens 16, a focusing lens17, an aperture stop opening 18, and a CCD pickup element 19 or imagingelement. A zoom lens driving mechanism 20 includes a zoom motor, anddrives the zoom lens 16 in a direction along an optical axis. The zoomlens 16 optically zooms an object image focused on the CCD pickupelement 19. The focusing lens 17 is moved in the optical axis directionupon rotation of the focusing ring 7, and focuses object light on theCCD pickup element 19 in an in-focus position according to an objectdistance. A focusing ring sensor 7 a as shifting amount detector isassociated with the focusing lens 17, and detects a rotational shiftingamount of the focusing lens 17. An iris shifting circuit 21 in anaperture stop shifting mechanism changes a diameter of the aperture stopopening 18 defined in an aperture stop unit, and also shifts theaperture stop opening 18 in a direction toward and away from theaperture stop opening 18 within a plane perpendicular to the opticalaxis.

In FIG. 4, the aperture stop opening 18 is defined by a pair of aperturestop blades 25 and 26 in the aperture stop shifting mechanism. Rackportions 25 a and 26 a are formed with respectively the underside of theaperture stop blades 25 and 26. Iris motors 27 and 28 as blade actuatorsdrive respectively the aperture stop blades 25 and 26. Pinions 29 and 30are fastened on respectively output shafts of the iris motors 27 and 28,and meshed with the rack portions 25 a and 26 a. As the rack portions 25a and 26 a are driven by the pinions 29 and 30, the aperture stop blades25 and 26 move horizontally in an individual manner from one another, toadjust a diameter of the aperture stop opening 18 continuously, and toshift the aperture stop opening 18 for light amount gravity centers.

In FIGS. 5A and 5B, the aperture stop opening 18 is shiftable betweentwo light amount gravity centers P1 and P2, which are disposedsymmetrical to each other with respect to an optical axis. In FIG. 5A, astate of focusing light from an object point O1 to a pickup surfaceP_(I) by use of the focusing lens 17 is depicted. Also, a shift of theaperture stop opening 18 to the light amount gravity center P1 on aright side is depicted. A light line R1 from an object point O1 reachesa point S1 that is disposed on the pickup surface P_(I) and on theoptical axis A1. A light line R2 from an object point O2 that is fartherfrom the object point O1 intersects with the optical axis A1 in front ofthe pickup surface P_(I), and reaches a point S2 that is disposed on thepickup surface P_(I). A light line R3 from an object point O3 that isnearer from the object point O1 reaches a point S3 that is disposed onthe pickup surface P_(I) without intersecting with the optical axis A1.When the aperture stop opening 18 shifts to the light amount gravitycenter P2 on a left side, the light lines R1, R2 and R3 reach the pointsS1, S2′ and S3′ that are disposed on the pickup surface P_(I). See FIG.5B.

In FIG. 6A, light from the object point O1 is focused on the pickupsurface P_(I), to obtain an in-focus state. In FIG. 6B, light from theobject point O2 is focused at a point PF in front of the pickup surfaceP_(I), which is a front focus state. An image deviation G2 of an imagein the front focus state is a distance between the points S2 and S2′. InFIG. 6C, light from the object point O3 is focused at a point PR behindthe pickup surface P_(I), which is a rear focus state. The imagedeviation G2 in the front focus state is determined positive. An imagedeviation G3 in the rear focus state is determined negative. Accordingto the positive and negative directions, movement of the focusing lens17 can be indicated in a clarified manner.

If a distance from the aperture stop opening 18 to the pickup surfaceP_(I) is sufficiently smaller than a subject distance, two triangles areformed with a relationship approximated as similar to each other bystraight lines connecting centers of the aperture stop opening 18 set inthe plural positions and a light path of main light lines reaching thepickup surface P_(I). A ratio of the similarity between the trianglescan be obtained according to a shifted distance M of the back-and-forthshift of the aperture stop opening 18 and an image deviation G. This iseffective in obtaining the defocus amount or deviation of focus, namelya distance between the pickup surface P_(I) and a focal plane associatedwith each of subject distances. The defocus amount being obtained, adistance from a present position of the focusing lens 17 to an in-focusposition can be found.

In FIG. 7, the pickup data processor 12 is constituted by a pickup dataretrieving circuit 33 or brightness determiner, an image processingcircuit 34, a focus evaluation circuit 35 and an image outputtingcircuit 36. The pickup data retrieving circuit 33 includes an auto gaincontrol (AGC) unit 40 and a pixel mixing unit 41 with an adder as gaincontroller. The AGC unit 40 for amplification adjusts the gain toregularize an average level of an output signal of the CCD pickupelement 19, and interpolates brightness of each of the pixels. The pixelmixing unit 41 effects addition of brightness values of plural adjacentpixels in an image frame, substitutes the added brightness for initialbrightness of the plural adjacent pixels, to correct contrast of animage by lowering resolution. The AGC unit 40 and the pixel mixing unit41 are selectively operated according to an initially determinedsetting.

The image processing circuit 34 is constituted by a white balancecorrection unit 42, a gamma correction unit 43, and an A/D converter 44.The white balance correction unit 42 amplifies the pickup data accordingto predetermined gains for R, G and B, for adjustment of the whitebalance. The gamma correction unit 43 corrects the contrast gamma of thepickup data. After the correction, the pickup data is converted by theA/D converter 44 into a digital form of image data.

The focus evaluation circuit 35 has a shifted image memory 45 and adefocus determiner 46. The shifted image memory 45 stores two images offrames picked up in the course of shifting the aperture stop opening 18.The defocus determiner 46 analyzes two object images being stored, toobtain an image deviation between positions of the images by utilizingpixels. According to the image deviation, a defocus amount or deviationof focus is calculated, and sent to the image outputting circuit 36.

The image outputting circuit 36 is constituted by a split imagecombination unit 47 and a shift calculation unit 48. The split imagecombination unit 47 receives data of images of the two frames read fromthe shifted image memory 45, subjects those to trimming processing, andcombines them together, for conversion to split images for the purposeof displaying a state of focusing. The shift calculation unit 48 treatsa change in the deviation of the focus according to rotation of thefocusing ring 7, and converts the change into a shifting amount in thedisplayed split images.

The display controller 13 receives data of an image output by the imageprocessing circuit 34 and split sample images output by the imageoutputting circuit 36, and causes the monitor display panel 8 and/or theviewfinder 9 to indicate those images. In FIG. 8, the entirety of theframe is constituted by a main region or background region 51 orphotographic field display region, and a focus adjusting region 50surrounded by the background region 51. When a center of the aperturestop opening 18 is located on the optical axis, the background region 51displays an object image being picked up. The focus adjusting region 50is constituted by first and second split regions. A split sample image52 a in the first split region is a portion of a right-shifted objectimage 52. A split sample image 53 a in the second split region is aportion of a left-shifted object image 53. Note that the right-shiftedobject image 52 is obtained when the aperture stop opening 18 is shiftedto the left as viewed from a user holding the camera. The left-shiftedobject image 53 is obtained when the aperture stop opening 18 is shiftedto the right. This is the result of the rear focus condition.

Note that, in uppermost portions of FIG. 8, the contours of the rightand left-shifted object images 52 and 53 are clearly depicted for thepurpose of understanding, but are actually in an unsharply focused formbecause of the step prior to the focus adjustment.

Referring again to FIG. 6B illustrating the front focus point PF, thefocal plane of the focusing lens 17 is located in front of the pickupsurface P_(I) of the CCD pickup element 19. According to the shift ofthe aperture stop opening 18 to the right, object light becomes incidentupon a position offset to the left on the pickup surface P_(I), so thatthe split sample image comes to have a form in which an originalposition of the object is shifted to the right. Similarly, the splitsample image according to the shift of the aperture stop opening 18 tothe left comes to have a form in which the original position of theobject is shifted to the left.

Referring now to FIG. 6C illustrating the rear focus point PR, the focalplane of the focusing lens 17 is located behind the pickup surface P_(I)of the CCD pickup element 19. According to the shift of the aperturestop opening 18 to the right, object light becomes incident upon aposition offset to the right on the pickup surface P_(I), so that thesplit sample image comes to have a form in which an original position ofthe object is shifted to the left. Similarly, the split sample imageaccording to the shift of the aperture stop opening 18 to the left comesto have a form in which the original position of the object is shiftedto the right.

When the focusing ring 7 is rotated manually, information of a rotatingamount of the focusing ring 7 is detected by the focusing ring sensor 7a, and sent into the shift calculation unit 48 by the main controller11. According to the rotating amount, the shift calculation unit 48calculates an amount of shifting the displayed split sample images. Inaccordance with a result from the shift calculation unit 48, the splitimage combination unit 47 changes positions of trimming processing forthe images of the two frames stored in the shifted image memory 45,newly obtains a secondary combination of the split sample images, andoutputs information of the combination to the display controller 13.Each time that the focusing ring 7 is rotated, the split sample images52 a and 53 a in the focus adjusting region 50 are displayed with ashift, and kept symmetrical with each other with respect to the verticalcenter line. If the defocus amount or deviation of focus decreases, adisplayed deviation between the split sample images decreases untilpositions of the split sample images coincide to display an in-focusstate. If the defocus amount increases, a displayed deviation betweenthe split sample images increases, to indicate that being out of focusbecomes more remarkable.

The operation of the embodiment is described with reference to FIG. 9.When the CCD pickup element 19 is driven, the camera starts picking upobject light from a photographic object. The pickup data retrievingcircuit 33 is supplied with pickup data of respectively frames at aconstant speed of picking up. The pickup data is subjected by the pickupdata retrieving circuit 33 to processing of amplification or pixelmixture per one frame, to correct brightness of the image. The pickupdata is output to the display controller 13, to cause a display panel todisplay the object image of the frames continuously as a result ofpicking up.

After pickup is started, the release button 5 is depressed halfway.Otherwise, the focusing ring 7 is rotated at a very small rotationalangle. This starts measurement of a defocus amount or deviation offocus. A shift starting signal is sent by the main controller 11 to theiris shifting circuit 21, which drives the iris motors 27 and 28 in sucha manner as to rotate the pinions 29 and 30 in the same rotationaldirection. The aperture stop blades 25 and 26 shift in the samedirection, to displace the position of the aperture stop opening 18laterally.

When shifting of the aperture stop opening 18 is started, the displaycontroller 13 causes the display panel to display the object image in afrozen form. At first, the iris shifting circuit 21 shifts the aperturestop opening 18 to the right. When the aperture stop opening 18 hasmoved at a predetermined distance, the shifting to the right is stopped.Then pickup data output by the CCD pickup element 19 is sent to thefocus evaluation circuit 35, to write the data of the left-shiftedobject image 53 to the shifted image memory 45. This is a state at thetime of the rear focus. In the case of the front focus, a right-shiftedobject image is written.

Then the iris shifting circuit 21 shifts the aperture stop opening 18 inthe direction to the left. The aperture stop opening 18 is moved to aset position that is symmetrical to the right-side set position withrespect to the optical axis. Upon the stop of the shift to the left,pickup data output by the CCD pickup element 19 is sent to the focusevaluation circuit 35, to write data of the right-shifted object image52 to the shifted image memory 45. This is because of the rear focus. Inthe case of the front focus, a left-shifted object image is written.

The aperture stop opening 18 is shifted back to the center or opticalaxis. The display panel is caused to restart displaying an object imagein a motion picture manner after ending displaying the frozen image. Inthe focus evaluation circuit 35, data of two frames of images stored inthe shifted image memory 45 is read, and sent to the defocus determiner46. The defocus determiner 46 checks and obtains an image deviation, andcalculates a defocus amount or deviation of focus according to the imagedeviation. The image outputting circuit 36 is supplied with thecalculated deviation of the focus as defocus information.

The split image combination unit 47 creates data of primary split sampleimages to be displayed in the focus adjusting region 50. The primarysplit sample images are output and sent to the display controller 13.The focus adjusting region 50 appears in the screen of the displaypanel. Upon rotation of the focusing ring 7, information of its rotatingamount is sent to the shift calculation unit 48. The shift calculationunit 48 calculates a deviation of displayed images according to theinformation of the rotating amount. Secondary split sample images arecreated by considering the deviation of the displayed images. Thesecondary split sample images are output and sent to the displaycontroller 13. Images are displayed in a split manner shifted inhorizontally symmetrical directions to the right and the left.

At each time that the focusing ring 7 is rotated, processing of moving asplit sample image is effected. When the focusing lens 17 comes near tothe in-focus position, a deviation between the split sample imagesdecreases. When the focusing lens 17 becomes in-focus, the split sampleimages coincide with one another. When the release button 5 is fullydepressed, a releasing operation signal is sent to the main controller11. The image data output by the image processing circuit 34 is sent andwritten to the image memory 14 in a form picked up at the releasingtime. After the writing, the focus adjusting region 50 disappears in thedisplay panel. Only the background region 51 remains indicated in thedisplay panel.

Note that, in the present embodiment, the aperture stop opening 18 isshifted between the two light amount gravity centers that arehorizontally symmetrical with one another. The focus adjusting region 50is defined to lie on the center of the frame. However, amounts ofshifting the aperture stop opening 18 may be asymmetrical in view of thehorizontal direction. The focus adjusting region 50 can be defined tolie in a position offset from the center of the frame. Furthermore, itis possible to add a structure to shift the aperture stop opening 18 ina vertical direction, so as to shift the aperture stop opening 18two-dimensionally. This is effective in defining the focus adjustingregion 50 in any suitable position offset from the center of the frame.

In the above embodiment, the object images picked up at the time ofmoving the aperture stop opening 18 are used to form split sampleimages. However, other methods for obtaining coincidence of images forthe purpose of focusing may be used, for example, a method of doubleimage coincidence. A reference image and a movable sample image may bedisplayed in an overlapped manner. The reference image can bepredetermined as a still image without shift. The movable sample imagemay be displayed with sufficient transmittance so that the referenceimage can be observed through the movable sample image. According tothis, a double image coincidence can be utilized for focusing operation.Furthermore, it is possible to use a selectable structure between thesplit sample image display and the double image coincidence.

It is conceivable to desire still higher precision in the focusing. Forthis purpose, a defocus amount or deviation of focus may be obtainedpreviously, so that a focused state can be indicated by an auxiliaryform of enlarging the indicated deviation between the split sampleimages. Any suitable structure of an auxiliary form may be used for thehighly precise focusing. For example, an auxiliary indicia, such astriangular or circular indicia, can be indicated in a moving mannerrelative to a reference image, without using the object image itself forthe auxiliary form. Also, it is possible in the present invention toinform an in-focus state, a front focus state and a rear focus state inan auxiliary manner, and to inform movement of the focusing lens towardand away from the in-focus position. To this end, plural light sourcesin a small size may be used to indicate changes in the focus in a visualmanner.

Note that the aperture stop opening is shifted repeatedly to the twolight amount gravity centers so as to pick up and store images. This iseffective in changing the split sample images 52 a and 53 a continuouslyin response to shifts of the focusing ring 7. The focusing ring 7 can bemanually operated until the forms of the sample images visually come tocoincide with one another for the purpose of focus adjustment.Therefore, it is possible in the manual focus camera not to install thedefocus determiner 46 and the shift calculation unit 48 as well as thefocusing ring sensor 7 a. The arithmetic operation of the phasedifference detection may not be effected. The focus may be adjusted onlyobserving the monitor display panel 8 or the viewfinder 9 and operatingthe focusing ring 7.

An autofocus camera according to one aspect of the invention isdescribed with reference to FIGS. 10–13. In FIG. 10, a digital stillcamera 101 of autofocus type includes a main controller 102, a pickupdata processor 103 as controller, a display controller 104, a recordingcontroller 105, and an operation panel 106 as mode switch. The recordingcontroller 105 controls recording of a motion picture image or stillimage to a video tape, memory card or the like. The operation panel 106supplies the main controller 102 with an operation signal which isgenerated upon operation of a recording button, a still image recordingbutton (not shown) or the like.

A CCD pickup unit 107 is constituted by a zoom lens 109, a focusing lens110, an aperture stop opening 111, and a CCD pickup element 112. A zoomlens driving mechanism 113 is provided with a zoom motor, operates tomove the zoom lens 109 in an optical axis direction, optically to changea size of an object image focused on the CCD pickup element 112. Afocusing lens driving mechanism 114 has a focusing motor, operates tomove the focusing lens 110 in the optical axis direction, to focusobject light on the CCD pickup element 112.

In FIG. 11, a pickup data retrieving circuit 125 or brightnessdeterminer includes an auto gain control (AGC) unit 131 and a pixelmixing unit 132 with an adder as gain controller. The AGC unit 131, inaddition to the auto gain control, also operates to amplify the pickupdata to ¼ as high as a reference level, and supplies the pixel mixingunit 132 with the data of the amplified level. The pixel mixing unit 132adds up brightness signals of four pixels adjacent in a 2×2 matrix form,and substitutes the brightness of the sum for the initial brightness ofthe four pixels. According to the pickup data supplied to the pixelmixing unit 132, the contrast of the image becomes four times as high asthe initial contrast, because the number of the pixels becomes ¼ as highas that at the time of pickup.

An image processing circuit 126 includes an image correction unit 133and an A/D converter 134. The image correction unit 133 subjects thepickup data after the brightness correction to the adjustment of thewhite balance and the correction of the contrast gamma. The A/Dconverter 134 converts the corrected pickup data into a digital form ofimage data. The digital image data is sent to a focus evaluation circuit127 and an image outputting circuit 128.

The focus evaluation circuit 127 includes an image comparator 135, adefocus determiner 136, and a contrast determiner 137. The imagecomparator 135 compares the reference pickup data with pickup dataobtained by each operation of pickup per frames, and obtains an imagedeviation as a difference between those in consideration of pixels.

The defocus determiner 136 receives the image deviations from the imagecomparator 135, and obtains horizontal image deviations due to theshifts of the aperture stop opening, and converts the horizontal imagedeviations to deviations of the focus. Also, the defocus determiner 136considers the deviations of the focus, and obtains a distance betweenthe present position of the focusing lens 110 and an in-focus position,so as to calculate a moving amount of the focusing motor for the purposeof moving the focusing lens 110 to the in-focus position. The contrastdeterminer 137 analyzes the distribution of the contrast of an imageaccording to the pickup data, to obtain a contrast evaluation result.

An image shake compensator 138 is incorporated in the image outputtingcircuit 128. The image shake compensator 138 is connected with the imagecomparator 135 for the purpose of image shake check, according to whicha position of an image is corrected by compensating for a deviation ofan object image in a horizontal direction upon shifting of the aperturestop opening 111 defined in an aperture stop unit, or compensating for atwo-dimensional shake of a hand holding the camera. The image comparator135 obtains image deviations between plural frames consecutive to oneanother in a time-sequential manner. To this end, a temporary memory 135a is used for storing pickup data of the plural images. In the imageshake compensator 138, those image deviations are subjected to imageshake check, so that the respective frames are subjected to the imageshake compensation in the case of occurrence of image shake.

The operation of the present embodiment is described now by referring toFIG. 12. Pickup in the CCD pickup element 112 is started. An irisshifting circuit 115 in an aperture stop shifting mechanism is suppliedby the main controller 102 with an exposure control signal, to drive thetwo aperture stop blades. The aperture stop opening 111 is set at asuitable diameter predetermined for the phase difference detection. Acomparator 125 a at the AGC unit 131 is utilized to evaluate objectbrightness by comparison with a threshold brightness. If the measuredobject brightness is suitable, then phase difference detection isstarted. If the object brightness is high in consideration of thethreshold brightness, then the aperture stop opening 111 is driven andset at a smaller diameter. If the object brightness is low inconsideration of the threshold brightness, then the aperture stopopening 111 does not change. An exposure is corrected in accordance witha designated state.

In the case of designating the brightness correction according to thegain adjustment, a brightness signal of the pickup data input by the AGCunit 131 is automatically amplified to the reference level. In the caseof designating the brightness correction according to the pixel mixture,at first the AGC unit 131 automatically amplifies a brightness signal ofthe pickup data to ¼ as high a level as the reference level. Then thebrightness signal is added up by the pixel mixing unit 132, and comessubstantially near to the reference level. In the case of designatingthe exposure control according to the fully open aperture stop, theaperture stop opening 111 is set in a fully open state with a largerdiameter than the diameter predetermined for the phase differencedetection.

The focusing is started when the exposure is suitable or after effectingthe brightness correction by the gain correction or pixel mixture. Themain controller 102 sends a rangefinding starting signal to the irisshifting circuit 115, which drives iris motors to shift the aperturestop blades in an aperture stop shifting mechanism in one commondirection. At first, the aperture stop opening 111 starts shifting tothe right to reach the light amount gravity center P1 for the phasedifference detection. The image comparator 135 obtains a deviation ofthe object image generated in the shift of the aperture stop opening111, and sends information of the deviation to the image shakecompensator 138. The image outputting circuit 128 supplies the displaycontroller 104 and the recording controller 105 with the pickup dataafter the image shake compensation. When the aperture stop opening 111becomes shifted to the light amount gravity center P1, then the maincontroller 102 sends a retrieval command signal to the image processingcircuit 126. Pickup data is written to the focus evaluation circuit 127as a first sample image for phase difference detection.

When the first retrieval of a sample image is ended, the main controller102 sends a changeover signal to the iris shifting circuit 115. The irisshifting circuit 115 changes over driving of the iris motors, to startshifting the aperture stop opening 111 to the left. While the aperturestop opening 111 shifts, an image shake is compensated for in a similarmanner to the shift to the right. When the aperture stop opening 111comes to the light amount gravity center P2, the main controller 102outputs a retrieval command signal, so a sample image is retrieved inthe focus evaluation circuit 127. When the second retrieval of thesample image is ended, the aperture stop opening 111 is shifted back tothe initial position defined about the optical axis A1.

The image comparator 135 compares the two sample images retrieved uponthe shifts of the aperture stop opening 111 toward the right and left,and calculates a deviation of the images related to the position. Theimage comparator 135 sends information of the position deviation of thesample images to the defocus determiner 136. The defocus determiner 136calculates a defocus amount or deviation of focus according to theposition deviation of the sample images and the moving amount of theaperture stop opening 111. Also, the defocus determiner 136 obtains adistance required for moving the focusing lens 110 to an in-focusposition by considering the defocus amount. The defocus determiner 136supplies the main controller 102 with information of a focusing lensmoving amount, to designate a direction and distance of moving thefocusing lens 110.

The main controller 102 sends a focusing control signal to a circuit inthe focusing lens driving mechanism 114 according to the information ofthe focusing lens moving amount. The circuit in the focusing lensdriving mechanism 114 drives the focusing motor according to the movingdirection and moving distance obtained by the defocus determiner 136.The focusing lens 110 is moved to the in-focus position along theoptical axis. Object light is picked up on the CCD pickup element 112 inthe in-focus state.

If the object brightness is a low brightness and if the fully openaperture stop is designated, then a command signal for the fully openaperture stop is sent by the main controller 102 to the iris shiftingcircuit 115. The aperture stop blades move to the fully open positions.The focusing lens 110 is moved in the optical axis direction. Thecontrast determiner 137 analyzes the distribution of the contrast of animage during adjustment of the focusing lens 110, and obtains a contrastevaluation result constituted by the finite difference between theminimum and maximum brightness levels of the pixels related to themeasurement. The main controller 102 stops driving the focusing lens 110in the position where the contrast evaluation result is maximized, tocomplete the focusing operation.

In FIG. 13, one preferred embodiment is illustrated, in which anaperture stop opening 141 defined in an aperture stop unit is shiftedtwo-dimensionally. Iris motors 142 and 143 as blade actuators aresupported on a holder frame 144. A rack portion 144 a is formed with alateral side of the holder frame 144. There is a motor 145, which has anoutput shaft with a gear 146 secured thereto. The rack portion 144 a ismeshed with the gear 146. To shift the aperture stop opening 141vertically is separate from its horizontal shift. A focusing spot orcenter of the focusing can be determined in any desired position insidethe pickup frame or pickup region.

Note that the pickup data processor 103 obtains an in-focus position byevaluating the deviation data between the first and second sample pickupdata. To this end, a table memory can be preferably used. Deviation datacan be previously obtained by conducting experiments. Data of in-focuspositions may be written to the table memory at addresses of thedeviation data.

In the above embodiment, the brightness is evaluated in three steps byevaluating the pickup data by use of high and low threshold brightness.For the comparison with the threshold brightness, the comparator 125 ais incorporated in the pickup data retrieving circuit 125.

Specifically, at first the pickup data is evaluated by comparison with ahigh threshold brightness. If the brightness according to the pickupdata is equal to or higher than the high threshold brightness, the firstand second sample pickup data are created and considered for focusadjustment. If the brightness according to the pickup data is lower thanthe high threshold brightness, then the pickup data is evaluated bycomparison with a low threshold brightness that is lower than the highthreshold brightness. If the brightness according to the pickup data isequal to or higher than the low threshold brightness, then the first andsecond sample pickup data are created after amplification by the gainadjustment, and considered for focus adjustment. If the brightnessaccording to the pickup data is lower than the low threshold brightness,then the fully open aperture stop is set. The gain adjustment issuppressed. The contrast is evaluated for the purpose of focusadjustment.

However, it is possible comprehensively to use the two methods of thegain adjustment and the sensitivity adjustment of the pixel mixture. Inthis case, a medium threshold brightness can be additionally used. Asthe high, medium, and low threshold brightness values are combined, thebrightness according to the pickup data is evaluated in four steps.

To be precise, if the brightness according to the pickup data is lowerthan the high threshold brightness, then the pickup data is evaluated bycomparison with a medium threshold brightness that is lower than thehigh threshold brightness. If the brightness according to the pickupdata is equal to or higher than the medium threshold brightness, thenthe first and second sample pickup data are created after amplificationby the gain adjustment, and considered for focus adjustment. If thebrightness according to the pickup data is lower than the mediumthreshold brightness, then the pickup data is evaluated by comparisonwith a low threshold brightness that is lower than the medium thresholdbrightness. If the brightness according to the pickup data is equal toor higher than the low threshold brightness, then the first and secondsample pickup data are created after amplification in the pixel mixturefor the sensitivity adjustment, and considered for focus adjustment. Ifthe brightness according to the pickup data is lower than the lowthreshold brightness, then the fully open aperture stop is set. Thesensitivity adjustment in the pixel mixture is suppressed. The contrastis evaluated for the purpose of focus adjustment.

Furthermore, only one value of threshold brightness may be used. Thebrightness according to the pickup data can be evaluated only in twosteps. Specifically, the pickup data is evaluated by comparison with athreshold brightness. If the brightness according to the pickup data isequal to or higher than the threshold brightness, then the first andsecond sample pickup data are created after amplification by the gainadjustment, and considered for focus adjustment. If the brightnessaccording to the pickup data is lower than the threshold brightness,then the fully open aperture stop is set. The gain adjustment issuppressed. The contrast is evaluated for the purpose of focusadjustment.

Another preferred digital still camera is described with reference toFIGS. 14–17, in which a moving object can be focused easily with asimple structure. Elements similar to those of the above embodiments aredesignated with identical reference numerals.

In FIG. 14, a pickup data retrieving circuit 225 outputs pickup data. Aframe memory 226 stores the pickup data from the pickup data retrievingcircuit 225 for the purpose of comparing images. Plural frames can bestored in the frame memory 226. When the number of the frames to bewritten to the frame memory 226 becomes over the maximum number ofwriteable frames of the frame memory 226, then the stored frames areoverwritten according the time sequence of writing. To be precise, onenewest frame is written at the same time as the oldest one of all thestored frames is deleted. The image comparator 135 reads images of twoframes from the frame memory 226, and obtains a deviation between theimages per pixels. The image comparator 135, obtaining the deviation ofthe images of the two frames, operates for outputting data for detectionof image shake derived from shift of the aperture stop opening 111 ormanual camera shake of a user's hand, and operates for outputting datafor measuring a focus deviation by obtaining a deviation between sampleimages according to setting of the aperture stop opening 111 in the twolight amount gravity centers.

A focus evaluation circuit 228 is constituted by the contrast determiner137 and the defocus determiner 136. The contrast determiner 137 readsframe data of the frames from the frame memory 226 sequentially,analyzes changes in the contrast by comparison between the frames, andoutputs a contrast detection signal of which a value is either one of acontrast being set higher and a contrast being set lower. The contrastdetection signal is sent to the main controller 102, which drives andadjusts the focusing lens 110 to set the contrast high.

The defocus determiner 136 obtains a defocus amount or deviation offocus according to the focus deviation measuring data output by theimage comparator 135, and calculates a moving amount for the focusinglens 110. The focus deviation measuring data is constituted by firstimage deviation information derived from horizontal shifting of theaperture stop opening 111, and second image deviation informationderived from movement of an object to be picked up. The defocusdeterminer 136 considers a finite difference between the first imagedeviation information and the second image deviation information, andobtains image deviation information relevant to disparity of view of theaperture stop opening 111. The disparity information of view isconverted to a defocus amount, to obtain a driving amount of thefocusing lens 110.

The operation of the present embodiment is described now with referenceto FIG. 15. The main controller 102 executes a sequence of one of thefocus control according to the contrast measurement and the focuscontrol according to the phase difference detection. If the focuscontrol of the contrast measurement is designated and executed, thefocusing lens driving mechanism 114 moves the focusing lens 110 finelyat a very small amount. The contrast determiner 137 compares images readfrom the frame memory 226, and responsively obtains changes in thecontrast due to the fine movement of the focusing lens 110.

In the case of the focus control according to the phase differencedetection, the iris shifting circuit 115 drives the iris motors to shiftthe aperture stop blades in one common direction. The aperture stopopening 111 starts shifting to the right, and reaches the light amountgravity center P1 for the phase difference detection. The imagecomparator 135 obtains a deviation of the object light generated duringthe shift of the aperture stop opening 111, and sends the data for theimage shake detection to the image shake compensator 138. The imageshake compensator 138 corrects the position of the images according tothe image shake detection data. The image data after the image shakecompensation is output to the display controller 104 and the recordingcontroller 105. If it is detected that an contour of the photographicobject is unsharp and out of focus, then the aperture stop opening 111is driven to reduce the diameter of the aperture stop.

When the center of the aperture stop opening 111 reaches the lightamount gravity center P1, the iris shifting circuit 115 drives the irismotors in the reverse direction, to start shift to the left. While theaperture stop opening 111 is moved, an image shake is compensated for inthe same manner as the shift to the right. When the center of theaperture stop opening 111 reaches the light amount gravity center P2,the aperture stop opening 111 starts being shifted to the right for asecond time. Upon completion of the first shifts to the right and thento the left, the image comparator 135 compares images having been pickedup in setting the aperture stop opening 111 in the two light amountgravity centers for the phase difference detection. The image comparator135 obtains a first shifting deviation of images according to the firstshift of the aperture stop opening 111, and outputs the first shiftingdeviation to the defocus determiner 136.

When the aperture stop opening 111 reaches the light amount gravitycenter P1 again, the aperture stop opening 111 starts a second shifttoward the left. The image comparator 135 compares images picked up eachtime of setting the aperture stop opening 111 in the light amountgravity center P1, and obtains a first moving deviation of imagesgenerated by movement of an object during back-and-forth movement of theaperture stop opening 111. The image comparator 135 sends the obtainedfirst moving deviation to the defocus determiner 136.

When the aperture stop opening 111 reaches the light amount gravitycenter P2 again, the aperture stop opening 111 comes back to the opticalaxis in the initial state. The image comparator 135 obtains a secondshifting deviation of images according to the second shift of theaperture stop opening 111, and outputs the second shifting deviation tothe defocus determiner 136. Also, the image comparator 135 comparesimages picked up each time of setting the aperture stop opening 111 inthe light amount gravity center P2, and obtains a second movingdeviation of images generated by movement of an object duringback-and-forth movement of the aperture stop opening 111. The imagecomparator 135 sends the obtained second moving deviation to the defocusdeterminer 136.

Let a photographic object travel at a constant speed and straight from aright-side lower corner toward a left-side upper corner of a frame. InFIGS. 16 and 17, an image 250 is picked up when the aperture stopopening 111 is shifted toward the right. An image 251 is picked up whenthe aperture stop opening 111 is shifted toward the left. An image 252is picked up when the aperture stop opening 111 is shifted toward theright for a second time. An image 253 is picked up when the aperturestop opening 111 is shifted toward the left for a second time. Let Tseconds be a period of the back-and-forth shift of the aperture stopopening 111. The images 250–253 are picked up at a period of T/2seconds. A first shifting deviation SG1 is obtained at 16 a bycomparison between the images 250 and 251. A second shifting deviationSG2 is obtained at 16 b by comparison between the images 252 and 253.Also, a first moving deviation MG1 is obtained at 16 c by comparisonbetween the images 250 and 252. A second moving deviation MG2 isobtained at 16 d by comparison between the images 251 and 253.

Each of the two moving deviations MG1 and MG2 constitutes a differenceof the images caused by movement of the photographic object within Tseconds. Each of the two shifting deviations SG1 and SG2 constitutes adifference of the images caused by movement of the photographic objectwithin T/2 seconds. Therefore, it is possible to find disparity of viewgenerated by the horizontal shifting of the aperture stop opening 111 asthe moving deviation per T/2 seconds is calculated, and the unit movingdeviation is subtracted from the shifting deviation. According to thepresent embodiment, the two moving deviations MG1 and MG2 are the samein the direction and the size. As a result, straight movement of thephotographic object at the constant speed in parallel with the pickupsurface is found on the basis of analyzing the moving deviations. A halfof the first moving deviation MG1 can be subtracted from the firstshifting deviation SG1, to obtain the disparity of view.

The defocus determiner 136 calculates the defocus amount or deviation offocus according to the obtained disparity of view. Succeeding processesafter this are the same as those of the above embodiment.

Furthermore, a defocus amount can be obtained by extracting thedisparity of view due to the movement of the aperture stop opening 111,because fine periodical shifts of images due to a camera shake withhands, irregular shifts of images due to panning or the like can beeliminated from the images obtained each time of setting the aperturestop opening 111 in the light amount gravity centers. If an objecttravels straight at a constant speed, the shift of the images can beseparated because the aperture stop opening 111 can be shifted back andforth for two times. However, the time of the back-and-forth shifts ofthe aperture stop opening 111 can be determined greater, to predict fineperiodical shifts or irregular shifts of images, so as to eliminateinfluence of such shifts from the focusing.

Note that, in the case of considering movement of a photographic objectin the optical axis direction, it is possible to effect the phasedifference detection repeatedly for continuous autofocus control. Also,changes in the in-focus position can be sampled in a time-sequentialmanner, for the purpose of the moving body predicting autofocus controlin consideration of time lag due to driving of the focusing lens. If theobject distance changes during shifts of the aperture stop opening, noerror will occur in detecting an image deviation in the case ofsufficiently small changes in a magnification of the object image on apickup surface. However, it is possible to detect a portion of an objectimage in the vicinity of the center of the pickup surface. This iseffective in reducing a change in the magnification of the object image,so that a width of changing the object distance capable of detecting animage deviation can be enlarged.

Although the present invention has been fully described by way of thepreferred embodiments thereof with reference to the accompanyingdrawings, various changes and modifications will be apparent to thosehaving skill in this field. Therefore, unless otherwise these changesand modifications depart from the scope of the present invention, theyshould be construed as included therein.

1. A manual focus device for a camera, including an aperture stop unitfor limiting a light amount of object light from a photographic objectby changing an opening size on a lens optical axis, a taking lenssystem, including a focusing lens for moving on said lens optical axisby manual operation, and for being set in an in-focus position accordingto an object distance, to condense said object light on a focal plane, apickup element, disposed on said focal plane, for outputting pickup databy picking up said object, said manual focus device comprising: anaperture stop shifting mechanism for setting said aperture stop unit ata first light amount gravity center by shifting said aperture stop unitin a first direction on a plane perpendicular to said lens optical axis,for setting said aperture stop unit at a second light amount gravitycenter by shifting said aperture stop unit in a second direction that isreverse to said first direction, wherein said first and second lightamount gravity centers are equidistant from said lens optical axis; animage memory for storing first and second sample pickup data obtained bypicking up said object in said pickup element through said aperture stopunit when said aperture stop unit is set at said first and second lightamount gravity centers; a display panel for displaying a combination offirst and second sample images according to said first and second samplepickup data, wherein positions of said first and second sample images,when said focusing lens is set in said in-focus position, coincide withone another, and when said focusing lens is set away from said in-focusposition, are offset from one another, wherein said aperture stopshifting mechanism has actuators for shifting said aperture stop unitand said actuators change an opening size of said aperture stop unit bysetting said aperture stop unit on said lens optical axis, to adjustsaid light amount for an exposure.
 2. A manual focus device for acamera, including an aperture stop unit for limiting a light amount ofobject light from a photographic object by changing an opening size on alens optical axis, a taking lens system, including a focusing lens formoving on said lens optical axis by manual operation, and for being setin an in-focus position according to an object distance, to condensesaid object light on a focal plane, a pickup element, disposed on saidfocal plane, for outputting pickup data by picking up said object, saidmanual focus device comprising: an aperture stop shifting mechanism forsetting said aperture stop unit at a first light amount gravity centerby shifting said aperture stop unit in a first direction on a planeperpendicular to said lens optical axis, for setting said aperture stopunit at a second light amount gravity center by shifting said aperturestop unit in a second direction that is reverse to said first direction,wherein said first and second light amount gravity centers areequidistant from said lens optical axis; an image memory for storingfirst and second sample pickup data obtained by picking up said objectin said pickup element through said aperture stop unit when saidaperture stop unit is set at said first and second light amount gravitycenters; a display panel for displaying a combination of first andsecond sample images according to said first and second sample pickupdata, wherein positions of said first and second sample images, whensaid focusing lens is set in said in-focus position, coincide with oneanother, and when said focusing lens is set away from said in-focusposition, are offset from one another, wherein said aperture stopshifting mechanism includes: first and second aperture stop blades,having inner curved edges opposed to each other, for defining an openinginside said inner curved edges; and first and second blade actuators forrespectively moving said first and second aperture stop blades in saidfirst and second directions.
 3. A manual focus device as defined inclaim 2, wherein each of said first and second blade actuators includes:a rack formed with one aperture stop blade included in said first andsecond aperture stop blades; a pinion meshed with said rack; and a motorfor rotating said pinion in forward and backward directions.
 4. A manualfocus device as defined in claim 1, wherein said display panel is anelectronic viewfinder for observing said object.
 5. A manual focusdevice as defined in claim 1, further comprising a defocus determinerfor detecting a phase difference between said first and second samplepickup data, so as to obtain defocus information representing an amountof a deviation of said focusing lens from said in-focus position.
 6. Amanual focus device as defined in claim 1, wherein when said aperturestop shifting mechanism is set at said first and second light amountgravity centers, said opening size of said aperture stop unit is smallerthan an opening size in a fully open state thereof.
 7. An autofocuscamera comprising: a taking lens system, including a focusing lensmovable on a lens optical axis, for being set in an in-focus positionaccording to an object distance, to condense object light from aphotographic object on a focal plane; a lens driving mechanism formoving said focusing lens on said lens optical axis; a pickup element,disposed on said focal plane, for outputting pickup data by picking upsaid object; an aperture stop unit for limiting a light amount of saidobject light; an aperture stop shifting mechanism for setting saidaperture stop unit at a first light amount gravity center by shiftingsaid aperture stop unit in a first direction on a plane perpendicular tosaid lens optical axis, for setting said aperture stop unit at a secondlight amount gravity center by shifting said aperture stop unit in asecond direction that is reverse to said first direction, wherein saidfirst and second light amount gravity centers are equidistant from saidlens optical axis, and wherein said pickup element outputs first andsecond sample pickup data by picking up said object through aperturestop unit when said aperture stop unit is set at respectively said firstand second light amount gravity centers; and a controller for obtainingsaid in-focus position by a process of comparison and evaluation of saidfirst and second sample pickup data, and for actuating said lens drivingmechanism in accordance therewith, wherein said aperture stop shiftingmechanism has actuators for shifting said aperture stop unit and saidactuators change an opening size of said aperture stop unit by settingsaid aperture stop unit on said lens optical axis, to adjust said lightamount for an exposure.
 8. An autofocus camera as defined in claim 7,wherein said controller includes: an image comparator for obtaining aphase difference by comparison between said first and second samplepickup data; and a defocus determiner for obtaining defocus informationrepresenting an amount of a deviation of said focusing lens from saidin-focus position according to said phase difference.
 9. An autofocuscamera as defined in claim 8, further comprising a gain controller foramplifying said pickup data in consideration of a predeterminedbrightness level, to supply said controller therewith.
 10. An autofocuscamera as defined in claim 9, wherein when said aperture stop shiftingmechanism is set at said first and second light amount gravity centers,said opening size of said aperture stop unit is smaller than an openingsize in a fully open state thereof.
 11. An autofocus camera as definedin claim 9, further comprising a comparator for determining whetherbrightness according to said pickup data is a low brightness bycomparison with threshold data; wherein when said brightness accordingto said pickup data is said low brightness, said gain controlleramplifies said first and second sample pickup data.
 12. An autofocuscamera as defined in claim 9, further comprising an adder for adding upsaid pickup data of N adjacent pixels to obtain pixel mixing pickupdata, for image reduction at a ratio of 1/N.
 13. An autofocus camera asdefined in claim 12, further comprising a mode switch for setting a highcontrast mode upon being tuned on; wherein said adder is operated uponsetting said high contrast mode, to obtain said pixel mixing pickupdata.
 14. An autofocus camera as defined in claim 8, wherein saidaperture stop shifting mechanism includes: first and second aperturestop blades, having inner curved edges opposed to each other, fordefining an opening inside said inner curved edges, wherein saidactuators are first and second blade actuators which respectively movesaid first and second aperture stop blades in said first and seconddirections.
 15. An autofocus camera as defined in claim 14, wherein eachof said first and second blade actuators includes: a rack formed withone aperture stop blade included in said first and second aperture stopblades; a pinion meshed with said rack; and a motor for rotating saidpinion in forward and backward directions.
 16. An autofocus camera asdefined in claim 15, wherein said first and second directions arehorizontal.
 17. An autofocus camera as defined in claim 8, furthercomprising: a comparator for determining whether brightness according tosaid pickup data is a low brightness by comparison with threshold data;a contrast determiner for outputting contrast information according tosaid pickup data; wherein when said brightness according to said pickupdata is said low brightness, said controller inhibits said aperture stopshifting mechanism from shifting toward said first and second lightamount gravity centers, causes said aperture stop shifting mechanism toopen fully said aperture stop unit about said lens optical axis, movessaid focusing lens, and checks a change in said contrast information inmoving said focusing lens, to determine said in-focus position inaccordance therewith.
 18. An autofocus camera as defined in claim 17,wherein said contrast information is a finite difference between maximumand minimum brightness levels of an image according to said pickup data,and when said finite difference is greatest, then said focusing lens isjudged as set in said in-focus position.
 19. An autofocus camera asdefined in claim 8, further comprising: a temporary memory for storingsaid pickup data of one frame by overwriting with said pickup data of aframe preceding to said one frame upon outputting of said pickupelement; said image comparator further compares said one and precedingframes being consecutive, and outputs time-sequential comparisoninformation; an image shake compensator for subjecting said pickup datato image shake compensation according to said comparison information.